Effects of Interfacial Phases on Bond Strength of Diffusion-Bonded Joints of Al-X Binary Alloys (X=Mg, Si, Mn, Zn, Cu). Diffusion-Bonding Mechanism of Al Alloys by Transmission Electron Microscopy. (Report 6).

On tool stirring action in friction stir welding of work hardenable aluminium alloys

“…They suggested that a so called zigzag line remained as a mark of the oxide layer in the cross-sectional stir zone for FSW parameters introducing low heat generation into the material. They concluded, in agreement with further researches, 16,17 that the zigzag line in the stir zone did not affect mechanical properties of the weld. Different studies, [17][18][19] conducted from the chemical point of view, reported that the amorphous Al 2 O 3 oxide in Al-Mg alloys easily changes into crystalline AlMg 2 O 4 or MgO phases during long time heating such as sintering and diffusion bonding.…”

“…They concluded, in agreement with further researches, 16,17 that the zigzag line in the stir zone did not affect mechanical properties of the weld. Different studies, [17][18][19] conducted from the chemical point of view, reported that the amorphous Al 2 O 3 oxide in Al-Mg alloys easily changes into crystalline AlMg 2 O 4 or MgO phases during long time heating such as sintering and diffusion bonding. Therefore, there is a possibility that thermal cycle of FSW changes surface oxide layer from amorphous Al 2 O 3 to the crystalline phases.…”

“…For this reason, to evaluate the behaviour of an oxide layer on the initial butt surface during FSW, the microstructure in the root of friction stir weld AA5052 was observed by electron microscope TEM evaluating the material density. 17 In this paper the authors have compared different solid state bonding conditions experimentally obtained at the varying of the main process parameters for FSW butt joints in AA5754-H111 aluminium alloy. In particular, an experimental campaign was carried out with the aim to identify a process parameters window within which optimal joint mechanical resistance can be found.…”

“…However, analysis was not complete because the investigation was conducted by an optical micrograph, uneffective to identify the oxide particles. For this reason, to evaluate the behaviour of an oxide layer on the initial butt surface during FSW, the microstructure in the root of friction stir weld AA5052 was observed by electron microscope TEM evaluating the material density 17…”